In various operations taking place under the water surface, especially in connection with oil or gas wells, one needs to provide electrical and/or optical connection to various equipment. Such equipment can for instance be a flow meter for monitoring the flow of hydrocarbons in a pipe, a temperature gauge, a pressure gauge, etc. Such connections may also be needed on order to actively control equipment such as valves, or control devices such as microcontrollers.
For such under water connections, specially adapted connectors are known. For instance, patent publication U.S. Pat. No. 5,772,457 describes a submersible electrical connector system. Here, electrical conductors extend in an inner chamber of the housing. The chamber is filled with a dielectric fluid. By arranging a bladder which constitutes a part of the chamber periphery, the chamber is pressure balanced with respect to the external hydrostatic pressure.
French patent application FR 2576718 describes another setup for achieving such pressure compensation. This publication describes a plug connection for interconnection to cables. Here, each facing plug part (11, 10) exhibit an inner chamber filled with a dielectric fluid (131, 132). The chambers are partly surrounded by elastic membranes (161, 162) that will transmit any hydrostatic surrounding pressure to said chambers. Such a setup will reduce the tendency of ambient water to penetrate into the plug parts.
In conditions where electrical conductors are led through a high pressure barrier, conventional elastic seals are not appropriate for withstanding the pressure difference for 20 or 30 years, which is normal design lifetime for permanent subsea installations. In such cases, a penetrator is commonly used. The penetrator can comprise glass that surrounds electrical conductors that extend from one end of it to the other. Since the penetrator shall withstand a large pressure difference and since it is made of glass, which is rather brittle compared to metal, the penetrator cannot tolerate much mechanical stress from the conductors. Such mechanical stress must therefore be accounted for with other means.
FIG. 1 shows such a means. This is an electrical wet-mateable connector housing available from the applicant (Roxar AS) and constituting a relevant prior art with to respect to the present invention. The housing comprises a penetrator adapted for constituting a high pressure barrier. On the right hand side of the penetrator, electrical conductors extend into an internal housing compartment. In use, the appropriate conductors are connected to additional electrical conductors extending towards the right and to a part of the housing that is adapted for receiving a wet-mateable counterpart of the connector. The details of this will be explained in further detail with reference to the other drawings. In the said inner compartment of the housing, there is arranged an electrically isolating liquid, such as an oil. To avoid water (or other external fluid) to penetrate into the inner compartment, the compartment is pressure compensated (pressure balanced) with respect to the outer hydrostatic pressure. In the top part of the housing shown in FIG. 1, there is arranged a piston which freely can adapt an equilibrium position where the pressure of the inner compartment equals the external hydrostatic pressure. Thus in this solution, the penetrator is not mechanically challenged, as the mechanical stress is absorbed by the receiving part of the housing. Moreover, water will not penetrate into the inner compartment.
The known solution illustrated in FIG. 1 has proven to function well. However, with the present invention there is suggested a less complex, lighter and more reliable manner for the desired pressure compensation and absorbance of any mechanical stress. Moreover, the present invention also provides advantages with regard to galvanic corrosion, as will be explained further below.